A tunnel magnetoresistive element (TMR) includes a pinned magnetic layer in which a magnetization direction is pinned (fixed), a free magnetic layer in which a magnetization direction changes depending on an external magnetic field, and an insulating layer between the pinned magnetic layer and the free magnetic layer, and forms a magnetic tunnel junction (MTJ). The resistance of the insulating layer changes by the tunnel effect depending on the angle between the magnetization direction of the pinned magnetic layer and the magnetization direction of the free magnetic layer. Such a tunnel magnetoresistive element is used in a magnetic memory, a magnetic head, a magnetic sensor, and the like.
In a magnetic sensor based on the principle of the TMR, a huge TMR ratio can be realized by magnetic annealing of the stack structure of the MTJ portion (CoFeB/MgO/CoFeB). At this time, it is important that B absorption layers (Ti, MgO, and the like) with a sufficient thickness made of a material that absorbs the diffusing B from the CoFeB layers are adjacent to the portion.
According to the invention disclosed in Patent Document 1, an MgO layer is positioned outside the MTJ in the MRAM.
According to the invention disclosed in Patent Document 2, a Ti layer is positioned in contact with a CoFeB layer(s) in a magnetic head or a memory.